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Utah State University DigitalCommons@USU Elusive Documents U.S. Government Documents (Utah Regional Depository) 1998 Climate Change and Utah United States Environmental Protection Agency Follow this and additional works at: http://digitalcommons.usu.edu/elusive_docs Part of the Environmental Sciences Commons Recommended Citation Environmental Protection Agency, United States, "Climate Change and Utah" (1998). Elusive Documents. Paper 56. http://digitalcommons.usu.edu/elusive_docs/56 This Book is brought to you for free and open access by the U.S. Government Documents (Utah Regional Depository) at DigitalCommons@USU. It has been accepted for inclusion in Elusive Documents by an authorized administrator of DigitalCommons@USU. For more information, please contact [email protected]. "':. Woited States Environmental Agency EPA 236~F-98'"007:z: September 1998 P""t""'tOl'' ' Climate Change::An'd Utah PB2001-101204 1111111111111111111111111111111111 The earth's climate is predicted to change because human activities are altering the chemical composition of the atmosphere through the buildup of greenhouse gases - primarily carbon dioxide, methane, nitrous oxide, and chlorofluorocarbons. The heat-trapping property of these greenhouse gases is undisputed. Although there is uncertainty about exactly how and when the earth's climate will respond to enhanced concentrations of greenhouse gases, observations indicate that detectable changes arc under way. There most likely will be increases in temperature and changes in precipitation, soil moisture, and sea level, which could have adverse effects on many ecological systems, as well as on human health and the economy. Emissions Of Greenhouse Gases Since the beginning of the industrial revolution, human activities have been adding measurably to natural background levels of greenhouse gases. The burning of fossil fuels - coal, oil, and natural gas - for energy is the primmy source of emissions. Energy burned to run cars and trucks, heat homes mld businesses, and power factories is responsible for about 80% of global carbon dioxide emissions, about 25% ofU .S. methane emissions, and about 20% of global nitrous oxide emissions. Increased agriculture and deforestation, landfills, and industrial production and mining also contribute a significant share of emissions. In 1994, the United States emitted about one-fifth of total global greenhouse gases. The Climate System Energy from the sun drives the earth's weather and climate. Atmospheric greenhouse gases (water vapor, carbon dioxide, and other gases) trap some of the energy from the sun, creating a natural "greenhouse effect." Without this effect, temperatures would be much lower than they arc now, and life as known today would not be possible. Instead, thanks to greenhouse gases, the earth's average tempera hIre is a more hospitable 60°F. However, problems arise when the greenhouse effect is enhanced by human-generated emissions of greenhouse gases. Global warming would do more than add a few degrees to today's average temperatures. Cold spells still would occur in winter, but heat waves would be more common. Some places would be drier, others wetter. Perhaps more important, more precipitation may come in short, intense bursts (e.g., more than 2 inches of rain in a day), which could lead to more flooding. Sea levels would be higher than they would have been without global warming, although the actual changes may vary from place to place because coastal lands are themselves sinking or rising. The Greenhouse Effect Some of the infrared radiation passes through the atmosphere, and some is absorbed and re-ernitled in all directions by greenhouse gas molecules. The effect of this is to warm the earth's surface and the lower atmosphere. Solar Concentrations Of Greenhouse Gases Since the pre-industrial era, atmospheric concentrations of carbon dioxide have increased nearly 30%, methane concentrations have more than doubled, and nitrous oxide concentrations have risen by about 15%. These increases have enhanced the heat-trapping capability ofthe earth's atmosphere. Sulfate aerosols, a common air pollutant, cool the atmosphere by reflecting incoming solar radiation. However, sulfates are short-lived and vary regionally, so they do not offset greenhouse gas warming. Although many greenhouse gases already arc present in the atmosphere, oceans, and vegetation, their concentrations in the future will depend in pa11 on present and futurc emissions. Estimating future emissions is difficult, because they will depend on demographic, economic, technological, policy, and institutional developments. Several emissions scenarios have been developed based on differing projections of these underlying factors. For exmnple, by 2100, in the absence of emissions control policies, carbon dioxide concentrations are projected to be 30150% higher than today's levels. Current Climatic Changes Global mean surface temperatures have increased 0.6-1.2°F between 1890 and 1996. The 9 warnlest years in this century all have occurred in the last 14 years. Ofthese, 1995 was the warmest year on record, suggesting the atmosphere has rebounded from the temporary cooling caused by the eruption of Mt. Pinatubo in the Philippines. Several pieces of additional evidence consistent with warming, such as a decrease in Northem Hemisphere snow cover, a decrease in Arctic Sea icc, and continued melting of alpine glaciers, have been con-oborated. Globally, sea levels have risen Source: U.S. Department of State (1992) ItlJS. REPRODUCED BY: u.s. Department of Commerce National Technical Information Service Springfield. Virginia 22161 Global Temperature Changes (1861-1996) well as a marked decrease in soil moisture over some midcontinental regions during the summer. Sea level is projected to increase by 6-38 inches by 2100. 0.6 0.4 f - - - - - - - - - - - - - - - - - - - f - - ' - - - 1 0.2 f - - - - - - - - - - - - - - - - - - - - - I " ' J - - - - 1 Calculations of regional climate changc are much less reliable than global ones, and it is unclear whether regional climate will become more variable. The frequency and intensity ofsomc extreme weather of critical importance to ecological systems (droughts, floods, frosts, cloudiness, the frequency of hot or cold spells, and the intensity of associated fire and pest outbreaks) could increase. o f-----------------------~_r--_r~---+----_4 ~ -0.2 -0.4 f - - - A . - - - r T - - - - / " " - ' - - - - - - - - - - - - - - 1 -0.6 'r+-~'---_4d_-\_____I_Id_-------------1 -0.8 f - - - - - - - - \ : + - - - - - - - - - - - - _ 4 Local Climate Changes Over the last century, the average temperature in Logan, Utah, has increased 1.4°F, and precipitation has increased by up to 20% in many parts of the statc. These past trends may or may not continue into the future. Source: IPCC (1995), updated 4-10 inchcs over the past cenhlry, and precipitation over land has increased slightly. The frequency of extreme rainfall events also has increased throughout much of the United States. Over the next century, climate in Utah may change even more. For example, based on projections made by the Intergovernmental Panel on Climatc Change and results from the United Kingdom Hadley Centre's climate model (HadCM2), a model that accounts for both greenhouse gases and aerosols, by 21 00 temperatures in Utah could increase by 3-4°F in spring and fall (with a range of I-6°F), and by 5-6°F in winter and summer (with a range of2-1 OOP). Precipitation is estimated to decrcase by 10% in summer (with a range of -5 to -20%), to increase by 10"1(, in spring (with a range of5-20%), to increase by 30% (with a range of 10-50%) in fall, and to increase by 40% in winter (with a range of20-70%). Other climate models may show different results, especially regarding estimated changes in precipitation. The impacts described in the sections that follow take into account estimates from different models. The amount of precipitation on extreme wet or snowy days in winter is likely to increase. The frequency of extreme hot days in summer would increase because of the general wanning trend. It is not clear how the severity of storms might be affected, although an increase in the frequency and intensity of winter storms is possible. A new international scientific assessment by the Intergovernmental Panel on Climate Change recently concluded that "the balance of evidellce suggests a discernible human illfluence on global climate. " Future Climatic Changes For a given concentration of greenhouse gases, the resulting increase in the atmosphere's heat-trapping ability can be predicted with precision, but the resulting impact on climate is more uncertain. The climate system is complex and dynamic, with constant interaction between the atmosphere, land, ice, and oceans. Further, humans have never experienced such a rapid rise in greenhouse gases. In effect, a large and uncontrolled planetwide experiment is being conducted. General circulation models are complex computer simulations that describe the circulation of air and ocean currents and how energy is transpOlted within the climate system. While uncertainties remain, these models are a powerful tool for studying climate. As a result of continuous model improvements over the last few decades, scientists are reasonably confident about the link between global greenhouse gas concentrations and temperahlre and about the ability of models to characterize future climate at continental scales. Precipitation Trends From 1900 To Present Trends/100 years +20% • +10% • Recent model calculations suggest that the global surface temperature could increase an average of 1.6-6.3°F by 2100, with significant regional variation. These temperature changes would be far greater than recent natural fluctuations, and they would occur significantly faster than any known changes in the last 10,000 years. The United States is projected to wann more than the global average, especially as fewer sulfate aerosols are produced. +5% • -5% 0 -10% -20% The models suggest that the rate of evaporation wiII increase as the climate warms, which will increase average global precipitation. They also suggest increased frequency of intense rainfall as PROTECTED UNDER INTERNATIONAL COPYRIGHT ALL RIGHTS RESERVED NATIONAL TECHNICAL INFORMATION SERVICE U.S. DEPARTMENT OF COMMERCE Source: Karl et al. (1996) 2 Reproduced from best available copy. 0 0 from Ogden to Provo. Groundwater levels, which are declining because oflarge withdrawals for public supply and for irrigation in southwestern Utah, could be lowered further. Energy development and mining operations in the eastern part of the state depend on adequate water supplies. Major water quality concerns such as the saline content of irrigation return flows and pollutant levels in urban strcams would be aggravated by lower flows and higher temperatures. Surface and groundwater have been fully allocated in many parts of Utah. Reductions in water availability could complicate water rights issues and interstate compacts. Changes in the timing and accumulation of snow could affect skiing conditions in positive and negative ways, such as the timing and length of season and snow depth. Human Health Higher temperatures and increased frequency of heat waves may increase the number of heat-related deaths and the incidence of heat-related illnesses. The elderly, especially those living alone, are at greatest risk. These effects have been studied only for populations living in urban areas; however, even those in rural areas may be susceptible. In Salt Lake City, one study estimates little change in heat-related deaths during the summer given a 3-4 OF wanning (the current population appears to be accustomed to intense, dry heat). This study also shows a slight increase in winter-related deaths. However, thc exact reasons for this increase are unknown. Climate change could increase concentrations of groundlevel ozone. For example, high temperatures, strong sunlight, and stable air masses tend to increase urban ozone levels. Currently, the Salt Lake City area is classified as a "moderate" nonattainment area for ozone. Wanning could worsen air quality further. Ground-level ozone is associated with respiratory illnesses such as asthma, reduced lung function, and respiratory intlammation. In a warmer climate, earlier and more rapid snowmelt, heavier rains, and the possibility of more rain could all contJibute to flooding, particularly in the winter and spring. Densely populated urban areas in the Wasatch Front are susceptible to springmeJt floods, and high lake levels around Utah and Great Salt lakes have caused considerable damage to farmland, wildlife habitats, industries, transportation routes, recreation facilities, and residential areas. Incrcased and more intense rains also could increase landslides and mudslides in the state's mountainous regions, as well as pollution in runoff from urban and mining areas. Upper and lower respiratory allergies are influenced by humidity. A 2°F wanning and wetter conditions could increase respiratory allergies. Agriculture Infected individuals can bring malaria to places where it does not occur naturally. Also, some mosquitoes in Utah can carry malaria, and others can carry western equine encephalitis, which can be lethal or cause neurological damage. If conditions become warmer and wetter, mosquito populations could increase, thus increasing the risk of transmission if these diseases are introduced into the area. Increased runofffrom heavy rainfall could increase water-borne diseases such as giardia, cryptosporidia, and viral and bacterial gastroenteritides. Developed counhies such as the United States should be able to minimize the impacts of these diseases through existing disease prevention and control methods. The mix of crop and livestock production in a state is influenced by climatic conditions and water availability. As climate warms, production patterns could shift nOlihward. Increases in climate variability could make adaptation by farmers more difficult. Warmer climates and less soil moisture due to increased evaporation may increase the need for irrigation. However, these same conditions could decrcase water supplies, which also may be needed by natural ecosystems, urban populations, industry, and other users. Understandably, most shldies have not fi.llly accountcd for changes in climate variability, water availability, crop pests, In 1993, hantavirus pulmonary syndrome emerged in Utah, and the deer mice that are the primary reservoir for the hantaviruses are prevalent in Utah. Long droughts punctuated by heavy rains can decrcase the predators (owls, snakes, and coyotcs) of rodents, and the heavy rains can provide the rodents with added food supplies (grasshoppers and pinon nuts). Changes In Agricultural Yield And Production Production Irrigated Yield 10 0 Water Resources OJ 0> c: Winter snow accumulation and spring snowmelt strongly affect Utah's rivers. A warnler elimate could result in less winter snowfall, more winter rain, and faster, earlier spring snowmelt. In the summer, without increases in rainfall of at least 15-20%, higher temperatures and increased evaporation could lower streamflows and lake levels. Less spring and summer recharge also could lower groundwater levels. Less water would be available to support irrigation, hydropower generation, public supply, fish and wildlife habitat, recreation, and mining. Concerns about adequate water supplies could be exacerbated along the highly populated and industrialized Wasatch Front, which oms -10 t1l .c: U ~ 0 -20 -30 ·40L---------------------------------~ Wheat • Barley Hay tiT = 9"F; tlprecip. = 19% _ Wheat Barley Hay t,T = 8"F; tlprecip. = 27% Sources: Mendelsohn and Neumann (in press); McCarl (personal communication) 3 changes in air pollution such as ozone, and adaptation by farmers to changing climate. Including these factors could change modeling results substantially. Analyses that assume changes in average climate and effective adaptation by fanners suggest that aggregate U.S. food production would not be harmed, although there may be significant regional changes. With changes in climate, the extent offorested areas in Utah could change little or decline by as much as 15-30%. The uncertainties depend on many factors, including whether soils become drier and, if so, how much drier. Hotter, drier weather could increase the frequency and intensity of wi ldfires, threatening both property and forests. Drier conditions would reduce the range and health of ponderosa and lodgepole forests, and increase their susceptibility to fire. Grassland, rangeland, and even desert could expand into previously forested areas. Milder winters could increase the likelihood of insect outbreaks and of subsequent wildfires in the dead fuel left after such an outbreak. These changes would significantly affect the character of Utah forests and the activities that depend on them. However, increased rainfall could reduce the severity of these effects. In Utah, production agrieulhlre is an $800 million annual industry, three-fourths of which comes from livestock, mainly cattle. About 80% ofthe farmed acres arc irrigated. The major crops in the state are wheat, barley, and hay. Climate change could significantly affect agricultural production, for example, reducing wheat yields by 10-30% as temperatures rise beyond the tolerance level ofthe crop. Irrigated barley, hay, and pasture yields, however, could rise by about 7%; un irrigated yields of those crops could rise by 3% or fall by 9%, depending on how climate changes. One model estimates that agricultural production of grain and forage crops could decline 5-30%. Fanned acres are projected to remain fairly constant. Livestock and dairy production may not be affected, unless summer temperatures rise significantly and conditions become significantly drier. Under these conditions, livestock tend to gain less weight and pasture yields decline, limiting forage. Ecosystems Utah is at the intersection of four unique regions: the basin and range country of the Great Basin, the alpine peaks ofthe Rocky Mountains, the canyon countly of the Colorado Plateau, and the Mojave Desert. This variety of habitats supports over 3,500 species of native plants and animals, making Utah the fifth-ranked state in the nation in terms of biodiversity. The Great Basin region alone contains a rich array of ecosystems, including playas and alkaline flats that are home to salt-tolerant plants, salt lakes and dunes, marshes that are crucial habitat tor migratOlY waterfowl, vast expanses of sagebrush, the pinon-juniper woodlands, the mountain islands of the Great Basin, aspen glens, and the subalpine forests that are home to the oldest living trees on the planet, 4,000-year-old bristlecone pines. The Great Salt Lake, the world's 33rd largest waterbody, is a migratory stopover and breeding site of international impOltance for a myriad of bird species, including Wilson's phalaropes, American avocets, whitefaced ibis, white pelicans, and the world's largest colony of Califomia gulls. Forests Trees and forests arc adapted to specific climate conditions, and as climate warms, forests will change. These changes could include changes in species composition, geographic range, and health and productivity. If conditions also become drier, the current range and density of forests could be reduced and replaced by grasslands and pasture. Even a wanner and wetter climate could lead to changes; trees that are better adapted to these conditions, such as fir and spruce, would thrive. Under these conditions, forests could become more dense. These changes could occur during the lifetimes oftoday's children, particularly if the change is accelerated by other stresses such as fire, pests, and diseases. Some of these stresses would themselves be worsened by a wanner and drier climate. The Great Salt Lake may be one of the most vulnerable wetlands in the United States to changing climate. A warmer climate would increase evaporation and, without offsetting increases in rainfall, the lake would shrink and the salinity levels would increase. These changes would have adverse impacts for migratory bird populations for which this ecosystem is crucial. The rangelands of the Great Basin are already threatened by the expansion of non-native weedy species such as European cheatgrass. Climate change could exacerbate such threats, because opportunistic exotic species are well-suited to take advantage ofthe ecosystem disturbances caused by warming temperatures, such as increases in the frequency and severity ofwilclfires. Climatic variability also could lead to increased susceptibility of rangelands to droughts, insect pest outbreaks, and floods. Streams, rivers, and other freshwater oases situated in this arid landscape are highly vulnerable to climate change, particularly to wanner and drier conditions. Coupled with increasing human demands on water resources, these changes could destroy or seriously degrade the few wetland habitats that exist in this state . Changes In Forest Cover Current • Tundra • Conifer Forest Ii Broadleaf Forest SavannalWoodland +10°F, +13% Precipitation • Shrub/Woodland .. Grassland II Arid Lands For further information about the potential impacts of climate change, contact the Climate and Policy Assessment Division (2174), U.S. EPA, 401 M Street Sw, Washington, DC 20460, or visit http://www.epa.gov/globa/warming/impacts. Sources: VEMAP Participants (1995); Neilson (1995) 4